1. Field of the Invention
The present invention relates to marking materials and, more particularly, is directed to fluorescent marking materials and a method for the manufacture thereof.
2. Description of the Prior Art
Marking crayons currently available on the market have met with limited success because they frequently exhibit less than favorable erasure characteristics. Such marking crayons are used for a variety of applications including children's toys. For example, erasable markers are used in back-lit bulletin boards. One of the disadvantages of currently available so-called erasable markers is that the marks produced by such markers frequently can not be erased without leaving a smeared surface which, in turn, makes viewing of subsequent writings difficult. As a result, users are often forced to clean-off an entire marked surface rather than amend only the relevant portions.
Attempts to produce high legibility markers having good erasure qualities have focused on the use of plasticizer or resin additives in conjunction with pigment materials. See U.S. Pat. Nos. 4,978,390 and 5,055,498. Also suggested have been formulations including, for example, vaseline and animal oils. See, e.g., U.S. Pat. Nos. 2,317,159 and 3,565,815. Unfortunately, however, none of these formulations produce a crayon having the requisite mechanical strength or desired erasure characteristics. More particularly, these formulations often produce crayons which are either overly soft or too brittle. Further, the marks they produce are effective only in the short-term due to rapid desiccation. Once the marks are desiccated, any attempt at erasure produces an unwanted, cloudy appearance on the writing surface.
A need has arisen for a marking material which exhibits improved writing and erasure characteristics.